Multiple wave band receiver



March 14, 1939. J, D RED 2,150,562

MULTIPLE WAVE BAND RECEIVER Filed Dec; 51, 1956 2 Sheets-Sheet 1 March 14, 1939. 2,150,562

MULTIPLE WAVE BAND RECEIVER Filed Dec. 31, 1936 2 Sheets-Sheet 2 Patented Mar. 14, 1939 UNITED STATES PATENT OFFICE John D. Reid, Philadelphia, Pa, assignor to Radio Corporation of America, a corporation of Delaware Application December 31, 1936, Serial No. 118,631

14 Claims.

The present invention relates to multiple waveband radio receivers, and has for its primary object to provide an improved multiple waveband tuning unit adapted to operate over an extended frequency range including an ultra high frequency band with improved stability and high gain.

The invention relates more particularly to a multiple wave-band high frequency tuning systern for superheterodyne radio receiveres and the like, wherein three or more tunable circuits are provided, and arranged to operate selectively over a plurality of differing frequency ranges or wave bands.

It is also an object of the present invention to provide improved and simplified switching means for a plurality of wave band tuning circuits, which may employ a minimum number and arrangement of contacts and circuit connections therefor.

In accordance with the invention, the antenna or radio frequency, first detector or mixer and oscillator inductances for a plurality of wave bands are arranged on separate coil forms, the inductance windings on each form being coaxial and compactly arranged as a single unit.

The switching arrangement is such that unused inductance and capacity elements are maintained in circuit and relatively few high signal potential points are Subjected to switching. The present switching system is arranged generally in accordance with, but provides certain improved features in, the multiple range tuning system as shown, described and claimed in a copending apr plication of Vernon D. Landon and William H.

Conron, Serial No. 61,778, filed January 31, 1936, Patent No. 2,113,157 issued April 5, 1938, for Coil system for multiple range radio receivers and the like, being assigned to the same assignee as this application. In that system successive portions of the secondary of a tuned coupling transformer are used as the primary in each higher frequency tuning band.

In the present system, a portion of the secondary windings included in tuning through one predetermined frequency range is used as the primary winding in the next higher frequency receiving band and properly resonated, and a plurality of the windings not used are maintained in the active circuits.

It is also a further object of the present invention, to provide an improved radio frequency and first detector multiple range tuning system, wherein a radio frequency amplifier may be used effectively in tuning over ultra high frequency wave bands.

In connection with the switching arrangement for the various coils in each stage, it is a further object of the present invention to provide a circuit wherein the trimmers or small adjustable tuning capacitors may each include one grounded electrode in direct connection with the metal chassis of the radio receiver or tuning unit.

The invention will, however, be better understood from the following description when considered in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings, Fig. 1 is a schematic circuit diagram of a tuning unit for a multiple range radio receiving system embodying the invention, and

Fig. 2 is a simplified and rearranged circuit diagram of a portion of the receiving system shown in Fig. 1, whereby the switching operations therein may more readily be understood.

Referring to Fig. 1, the tuning unit of the present example comprises a radio frequency amplifier tube 5, a first detector or mixer tube 6, an oscillator tube 1, and tuning means associated therewith, for selecting a signal received through a suitable input circuit such as an antenna circuit 4 and for producing therefroman intermediate frequency signal in the usual manner by interaction of the signal with locally generated oscillations from the oscillator.

The receiver or tuning unit includes an antenna or radio frequency tuning inductance unit 8 comprising a series of coils or sections 9, H], H, l2 and J3, and a separate high frequency unit comprising a coil or inductance l4, arranged to be connected with the control grid l5 of the radio frequency amplifier 5 and with a main variable tuning capacitor l6, together with a selected one of a plurality of grounded trimmer capacitors ll, through the operation of a simplified switch section IS. The trimmer capacitors for the high frequency coil I4 are indicated at IS.

The output circuit of the radio frequency amplifier 5, indicated at 20, is coupled to the signal grid 2! of the detector or mixer tube 6, through a second and similar coil system and switching arrangement comprising a tuning coil or inductance unit having coils or windings 22, 23, 24, 25, 26 and 2'! arranged in coaxial relation to each other in the order named, and as shown in the drawings. A high frequency tuning coil or inductance 28 is provided as a separate element. The main variable tuning capacitor for the signal input circuit for the detector or mixer 6 is indicated at 29 and the control switch section, which is the same as the control switch section I8, is indicated at 30. This switch serves to connect the various coil sections with the control grid 2|, with the main tuning capacitor 29, and the trimmer capacitors indicated at 3|, 32, 33,34, in a manner which will hereinafter be described.

The oscillator l is likewise provided with a series of coils in a similar coil unit 40, and a suitable control switch 4| therefor in connection with a high frequency tuning unit 42, and a main variable tuning capacitor 43, whereby the oscillator is tunable over a plurality of frequency ranges to provide the intermediate frequency signal.

The anode M of the oscillator is coupled to the control grid d5 through the coil system and connections provided by the switch section M. In the present example, oscillations are taken from the cathode lead 26 through an output lead t7 and are applied through a coupling capacitor 48 and a coupling resistor 49 to a second control grid 50 in the first detector or mixer tube, whereby the oscillations and signals are mixed to provide the intermediate frequency signal. The intermediate frequency output may then be applied to any suitable intermediate frequency amplifier (not shown) through the output circuit The leads for the output circuit and for supplying operating potentials to the unit indicated at 52 are connected to a suitable plug element 53 having contact terminals 54 connected with the leads 2 whereby the unit may be plug-connected with any radio receiver chassis for operation therewith. The antenna circuit '3 is connected directly with the turning unit through a high frequency primary 55 coupled to the coil M in the separate inductance unit and to the coil unit 9l3 through the switch section 18.

The oscillator circuit of this type is shown, described and claimed in my copending application Serial No. 38,762, filed August 31, 1935, for Frequency changer system for multiple range receivers. Accordingly, this circuit will not be further described. The switching operation, however, will further be described.

The three switch sections i8, 30 and 4| are arranged for gang or multiple operation to adjust the three circuits in proper relation to each other for operation over the same wave band to produce the desired intermediate frequency. The

-main variable tuning capacitors I6, 29 and 43 ered may be better understood, a present embodi-' ment of the circuit shown in Fig. 1 is required to cover the following bands of signal frequencies when tuned by a single unit-three gang variable tuning capacitor unit, comprising the elements "5, 29 and 43:

X band, -410 kc.

A band, 530-1800 kc. B band, 1800-6500 kc. 0 band, moo-22,000 kc. D band, 22,000-60,000 kc.

The coil sections in the drawings are given the above band designations in order that the operation of the system may be more readily understood, and likewise certain of the capacitors are given similar designations to indicate their circuit relation thereto in covering the various frequency bands. 7

frequency or D] band In this manner the total number of coils or windings and connections therefor are reduced, and this in turn simplifies the wiring to the range selector switch.

Each frequencyband is adjusted at the high frequency end of the tuning range by one or more of the trimmer or high frequency adjusting capacitors indicated at l 7, and these are provided preferably by capacitor units each having one electrode connected to ground or chassis. The trimmers are of the air-dielectric type and do not utilize mica under compression.

The coil structure or unit for the radio frequency stage includes the windings or coils 22-27 for the four lower frequency bands, and also includes a separate coil unit having the winding or coil 28 for the ultra high frequency or D band. The windings 26 and 27 are also utilized in connection with the ultra high frequency band, as will hereinafter be described. The coil structures for the antenna and radio frequency stage, comprising four tuning inductances on one coil form, operate to utilize the secondary coils or a portion of the secondary coils as the primary coils of the next higher frequency band. In this manner only five separate windings are required for the four wave bands and the switching operations are greatly simplified.

The X band primary and secondary windings or coils 9 and I0 in the antenna stage, and coils 22 and 23 in the radio frequency stage are universal type coils, while the remaining windings are preferably single layer coils arranged coaxially with the first mentioned coils on a common axis in spaced relation to each other. This system reduces the total number of different windings and results in having a low-loss primary and secondary for each wave band.

The D band coils for the antenna radio frequency and oscillator stages, indicated at M, 28 and @2, respectively, and their associated primary windings, consist of approximately a single turn of silver plated copper strap on relatively small coil forms having a diameter less than one inch, and are furthermore preferably associated closely with the corresponding section of the band selector range switch as indicated in the drawings, whereby the leads between the coils and the switch contacts are relatively short.

The general construction of the tuning unit and the construction and operation of the D band coils are shown, described and claimed in a copending application of John D. Reid and Loren R. Kirkwood, Serial No. 118,632, filed concurrently herewith, for Ultra high frequency coil system, and assigned to the same assignee as this application. Accordingly, further description of the D band coils is believed to be unnecessary.

The switching operation in the antenna and radio frequency stages is substantially the same, and it will be noted that the switch has the same contact arrangement in each section. The switching operation in connection with the radio frequency stage will be described in detail, with reference to the antenna stage, only to indicate corresponding differences in operation.

In the oscillator switching system the switch section 4I includes a moving contact elementBIl which successively engages contacts 6| connected with the grid ends of the A-A to D band coils 62, 63, 64, 65 and 42, respectively, providing connection with the tuning capacitor 43 and the grid 45 of the oscillator 'I through the lead 96.

At the same time a moving cathode contact 61 for the oscillator connects successively with a series of contacts 68 for the mid-tap connection on the corresponding coils 62 to 65 for the four lower frequency bands, and through a contact 69 with the D band primary coil 'I9which is coupled with the secondary 42s The oscillator plate connections are returned through ground indicated at H, I2 and I9.

An additional coil shorting contact I4 connected with ground is provided in the switch section to prevent absorption of energy from the active coils by the inactive coil elements.

The oscillator system utilizes a separate coil for each wave band and suitable contacts to effectively include a separate coil in circuit for each wave band, and accordingly, it does not concern the present invention except for the fact that the ultra high frequency coil unit is separate from the main inductance unit and that the wave band selector switch section 4| is provided with five consecutive positions of operation corresponding to the operating positions for the switching sections I8 and 39 in the antenna and radio frequency stages, whereby the switch sections may be interconnected for uni-control or gang operation in proper relation to each other for tuning all of the circuits in the same receiving band. Accordingly, further description of the oscillator switching is believed to be unnecessary.

The switching arrangement of the radio frequency amplifier stage will be more readily understood by referring to Fig. 2 together with Fig. 1. The circuit arrangement of: Fig. 2 is the same as that of Fig. 1, between the radio frequency amplifier and the detector 6, including the switching system and the coil arrangement, and with theswitch section diagrammatically represented whereby the contact operation may be more readily understood by linear operation of the contacts. However, the same reference numerals are applied to like parts in both figures.

The anode output circuit 29 of the radio frequency amplifier is connected through the coil 21, which is normally the C band primary coil, and a lead 15, with a second winding 16 which is normally the D band primary coil, and coupled with the secondary inductance 28.- These two windings comprise relatively few turns and have relatively low distributed capacity, particularly the coil I6.

The output anode circuit for the radio frequency amplifier 5 further is connected with the outer terminal 11 of the winding section. or coil 22 through a lead I8 leading from the coil 16, and the circuit is energized for anode potential supply through the coil 22 from a supply lead I9 in which is located a suitable filter resistor 89 provided with a b-y-pass filter capacitor 8 I. Anode current is derived from an input supply lead 82 which is connected with the plug connection 53.

The switch section 39 is arranged for rotary operation as shown in Fig. 1, and comprises a plurality of fixed contacts arranged in circular formation about a center of rotation 85. The contacts are designated by the reference numerals 96 to 91 inclusive, extending in a clockwise ing capacitor section 29.

direction about the center 85, with substantially equal angular spacing. An additional fixed arcuate contact 98 is provided in radially spaced relation to and associated with the contacts 86 to 89 inclusive, and on the same radius with the contact 99, and in radially spaced relation thereto, there is also provided a fixed contact 99, and a similar fixed'contact I99 on the same radius with the contact 91 and in radially spaced relation thereto.

The moving contacts of the switch comprise a bridging contact element I9I which moves between the arcuate contact 98 and the contacts 86 to 89, and between the contacts 99 and 99 in the fifth or D position, as the switch is rotated in a clockwise direction. A second movable bridging contact, arranged to move with the contact IN, is indicated at I92 and serves to connect the contacts 8'! to 9| inclusive, successively with the contacts 92 to 96 inclusive.

A third contact element I93, movable with the elements IM and I92, is arranged to provide a short circuit or bridging connection between the contacts 94 to 89 inclusive, and is provided with a contact member I94 which engages the contact I99 in the fourth and the contact 98 in the fifth position, as it is moved clockwise with the contacts I91 and -I92. These contacts are shown schematically, in linear form, in Fig. 2, and in that figure the same connections and sequence of connections are provided as in the switch of Fig. 1.

The trimmer capacitors 3| to 34, inclusive, are connected respectively with the contacts 92 to 95 inclusive, the contacts 9I and 96 being blank and without external connection.

The contact 86 is connected with the low frequency terminal end I95 of the coil section 23, and also is connected through a coupling capacitor I96 with the input terminal I! of the coil 22. The c'oils 23 to 26, inclusive, are connected in series as shown, and the successive inter-coil taps I91 to I99, inclusive, are connected respectively with the switch contacts-8'! to 89 inclusive. The high potential end terminal for the coil 26, indicated at I I9, is connected with the contact 99 and with the stator terminal III of the variable tun- Connection is also made from this lead with the signal input grid 2| of the detector 8 through the usual coupling capacitor H2 and grid resistor H3.

The ultra high frequency coil 28 is connected at its high potential side or terminal I I4 with the contact 99 through a short lead H5. The fixed contact I99 is connected through a capacitor II6 with the low potential side of the primary winding 21 and the high potential side of the primary winding I6, through the lead I5. The contact I99 is thus connected through the capacitor II6 between the two primary windings 2i and I6.

The contact 91 is connected to ground through a fixed capacitor of relatively low capacity I I7 and likewise the elongated fixed contact member 98 is connected to ground as indicated at I I8.

Referring to the antenna circuit switching arrangement in connection with the'switch section I8, it will be seen that the same circuit arrangement has been carried out. The antenna input circuit I is connected directly to the ultra high frequency primary 55 corresponding to the coil I6 in the radio frequency stage and thence through-a lead I29 to the input terminal I2I of the coil 9, and to a wave trap I22 which functions to reduce undesired intermediate frequency response in the antenna circuit. The terminal I2I is also connected to a terminal I23 corresponding to the terminal 91 in the radio frequency stage switch 30, and this operates to provide antenna connections to the windings III to I2, inclusive, which serve as primary windings for the higher frequency bands.

The winding II is provided with a center tap I24, which is connected through a lead I25 with a fixed contact I26, corresponding to the contact I013 in the switch section 30. In the antenna circuit arrangement, the contact I26 serves to! short-circuit the terminal I24 with the end terminals of the winding I I in the fourth or C band position of the switch I8, thereby to prevent the eifects of standing waves in the coil II from absorbing energy in the C band tuning range, particularly at the high frequency end thereof.

In all other respects, the operation of the switch section I8 and the connections provided thereby, are similar and for a similar purpose as the connections provided by the switch section 30, with the exception of the connections provided by the circuits connected with the winding 21 in the radio frequency stage for providing a compound primary in the two higher frequency bands C and D, as will be explained.

The wave band selector switch sections are shown in the operating position for receiving signals in the X band, and in this band, the coils 23 to 26 inclusive are connected in series and serve as the X band secondary winding, with the capacitor 3| in parallel with the coil 23 as a trimmer capacitor for adjusting the secondary circuit to resonance at the high frequency end of the tuning range. This practice is followed in the higher frequency bands and is eifective in providing resonance without having a' trimmer connection with the grid end of the secondary. The ground connection of the coil structure is at the low potential end, I05, of the X band secondary.

The coils 21, T6 and 22 are connected in' series, as a primary winding in the plate circuit of the radio frequency amplifier 5, with the winding 22 acting as the primary winding proper, to transfer energy by coupling with the combined secondary, particularly with the adjacent secondary coil 23. The windings 21 and I6 are substantially ineffective to provide any degree of coupling because of their low impedance at the low frequency of the X band tuning range. Also the secondary windings 24 to 26 inclusive provide a relatively small percentage of the total X band inductance. They are included in circuit, however, as are the primary windings 2'! and IE, to simplify the switching operations without introducing losses or other operating difiiculties.

The coil 22 serves as the main X band primary winding, and is tuned to a frequency below the X band by the shunt capacitor I66. This is in series with the capacitor 8| which is a relatively large capacitor. The capacitor I06 may have a capacity of substantially 560 mmf, while the by-pass BI may have a capacity of .01 mfd.

For the A band connections, the switch sections are advanced clockwise by the distance between two adjacent switch points. In the radio frequency stage, this places the winding 23' in parallel with the winding 22 through the capacitor I06 which provides a coupling capacitor between them for transferring energy from the plate circuit 20 of the amplifier 5 to the winding 23 as the primary winding for an A band. The A band secondary comprises the windings 24 to 2'6, inclusive, in series. The "X band secondary winding section 23 forms part of the A band primary, and is tuned below the "A band tuning range by the shunt capacitor III and the capacitor 34 in parallel, together with the distributed capacity'of the coil 22. The trimmer capacitor 32 is connected across the coil 24 in the A band secondary and serves to provide adjustment for the A band secondary resonance at the high frequency end of the band. As in the lower frequency band, the trimmer capacitor is not connected with the grid end of the coil. In this band also, the primary windings 21 and I6 are ineffective to transfer any appreciable energy to the A band secondary.

In considering the schematic circuit of Fig. 2, the moving connections or contacts ItBI, I02 and 1I03 are moved together in an upward direction,

The coil or winding 24 which was formerly a major portion of the A band secondary, now serves as the primary winding for the B and is resonated to the desired frequency below the B band tuning range by the primary tuning capacitor II! which is in shunt with the coil 24, and by the distributed capacity of the coil 22. The coil 23 is short-circuited by the switch to prevent absorption resonance effects. The primary winding 24 is capacity-coupled in the same manner as the preceding primary, to the plate circuit 20 in shunt with the coil 22, through the coupling capacitor I06. In this band also, the primary windings 2'! and I6 have very little effect in transferring energy to the secondary.

Advancing the switch to the C band, or fourth position, the winding 25 becomes the secondary, as the ground connection is then located at the terminal I09, between the coils 26 and 25, and the secondary is adjusted or trimmed at the high frequency end of the tuning range, by the trimmer capacitor 34 which is connected in shunt therewith. The coil 25, formerly the main portion of the B band secondary, now provides one portion of a compound primary winding, and is a low frequency primary winding for the C band. It is resonated to the proper frequency below the tuning range of the C band by the shunt primary resonating capacitor III and the distributed capacity of the coil 22.

The second portion of the primary is a high frequency primary coil provided by the winding 21. This is effective to increase the gain at the high frequency end of the C band, being coupled with the winding 26. The high frequency primary 2? is connected in series with the winding 25 through the capacitor H6 which renders the primary winding I6 ineffective by the shunt connection provided by the capacitor I I 8 and the capacitor II in series across it. This latter connection alsoplaces winding 22 in parallel with the low frequency primary 25, as above noted, which serves to lower the resonant frequency of the coil 25, by reason of the distributed capacity of the coil 22, and also serves to supply a positive potential to the plate of the R. F. tube 5.

The coils 23 and 24, being the X band and the A band secondary main portions, are shortcircuited by the switch to prevent energy absorption effects, and in this connection the high frequency primary winding 2'! has two functions.

In addition to providing high frequency primary circuit for the C band, it also reduces the resonance effect of the short circuit coil 24. Although the coil 24 has a direct short circuit across its terminal connections, it will absorb energy from the coil 26 or C band secondary at a frequency at which a standing wave is formed across the coil, which occurs at the high frequency end of the C band tuning range. The primary coil 2'! which is effectively in series between the anode circuit 20 and the A band coil 24, thus prevents absorption effects on the C band. The method of preventing this absorption in the antenna circuit through the tap connection on the corresponding coil I I has hereinbefore been described. Moving the switch now to the fifth position, for the ultra high frequency D band, the radio frequency stage is made to operate at the ultra high frequencies involved, and to increase the sensitivity and improve the image response ratio of the receiving system.

In this band, the separate secondary coil 28 is sh'unted across the coil 26 as a compound secondary or grid circuit winding and is adjusted at the high frequency end of the tuning range by the directly connected shunt trimmer capacitor I and a small fixed shunt capacitor I3I. The primary coils 21 and I6 are connected in series in this band, as in the previous bands. However, both are now effective to serve as high and low frequency primary windings respectively. The resonant frequency of the coil 21 is increased on this band for the reason that the coil I6 of low distributed capacity is in series with the coil 21, and the secondary coil 28 is connected in shunt across the coil 26 in the main tuning unit, so that both the primary windings are effective to transfer energy to the tuned secondary circuit. The coils for the B, A and X bands 25, 24 and 23, are short-circuited and connected to ground. 7

It will be noted that in all the five bands covered by the switching connections, the high frequency connection from the main variable tuning capacitor stator terminal I I I to the high potential terminal H9 of the main tuning inductance unit is not broken and is connected only in the ultra high frequency position with the secondary 28, whereby switching connections are reduced to a minimum in the high potential or grid end of the tuned secondary circuits.

Also the X band primary winding 22 serves as a choke coil for coupling the A and B band, and low frequency C band primaries to the radio frequency amplifier, and provides a distributed capacity for aiding in tuning the primaries, in addition to supplying a direct current path for the plate current to the radio frequency amplifier. This arrangement serves to maintain the X band primary in circuit without additional switching connections, which would otherwise be required to eliminate it, and use is made of the coil shorting connections to couple it to each active primary winding. I

Likewise, it will be seen that the switching connections are effected by three major moving contact elements, with the remaining contact elements all fixed, whereby the circuit connections are reduced to a minimum as portions of tuned high frequency circuits.

v Referring to Fig, 2 in particular, it will be seen that the switching connections comprise three major moving elements or members, the first of which is the grounding contact bridging member I8 I, which operates to ground the inter-coil taps as the latter progressively become the low potential ends of the secondary and primary windings, for the X, A, B and C bands. This contact member also serves to connect the D band coil to the grid circuit.

The second moving contact element is the trimmer selecting, contact-bridging member provided by the contact I02, which follows the grounding member and progressively connects the trimmers to the next higher coil tap for the X, A, B and C bands with the D band connection bridge because of the permanent trimmer on the coil 28 for the D band, and a primary resonating capacitor connecting and shortcircuiting control segment 503 which serves to connect the primary resonating capacitor II'I successively in the A, B and C bands. This arrangement of moving contacts greatly simplifies the switching operations.

The specific circuits and means employed in the C and D bands for resonating the compound primary windings and the use of the shunt connected compound secondary windings does not form a part of this invention, but is shown, described and claimed in an application of John D. Reid and Loren R. Kirkwood, Serial No. 139,122, for Coupling systems for multiple wave band circuits, filed April 27, 1937.

I claim: 7

1. In a multiple wave band radio receiving sys-.- tem, the combination with a primary circuit, and a tunable secondary circuit, of a tuning inductance comprising a series of coaxial winding sections connected at one end with said secondary circuit and having one of said sections at the opposite end connected with the primary circuit, means for progressively connecting a plurality of said sections each in parallel with said last named section to receive signal energy therefrom, said means comprising a switch having fixed contacts connected between said winding sections and a winding section short circuiting contact element movable with respect to and progressively in engagement with said contacts, a second contact element movable conjointly with the first contact element to progressively ground one ofconnecting said trimmer capacitors each with a selected one of said sections in the secondary circuit.

2. In a multiple wave band radio receiving system, the combination with a primary circuit, and a tunable secondary circuit, of a tuning inductance comprising a series of coaxial winding sections connected at one end with said secondary circuit and having one of said sections at the opposite end connected with the primary circuit, means for progressively connecting a plurality of said sections each in parallel with said last named section to receive signal energy therefrom, means for progressively connecting a plurality of said sections in series in the secondary circuit the number of sections in, the secondary circuit being progressively reduced as the primary circuit connection is progressively advanced toward the high frequency end of said tuning inductance, and means providing a high frequency and a low frequency primary winding efiectively coupled with said tuning inductance in the secondary circuit in an ultra high frequency and a high frequency tuning band.

3. In a multiple wave band switching system, the combination of a tuning inductance unit comprising a series of coaxial winding sections, a primary winding at one end of said unit, and switching means comprising three movable bridging contact elements, one of which provides a ground connection progressively along said inductance unitbetween said winding sections, a second one of which elements conjointly movable with the first element selectively provides trimming capacitor connections for said winding sections and progressively in advance of the grounding connection when advanced in the direction of the high frequency end of said inductance unit, and a third one of said contact elements providing a primary'resonating capacitor connection and short-circuiting means for said winding sections, means having a connection through said last named contact element for progressively coupling said winding sections in parallel with said primary winding, and a secondary circuit including a variable tuning capacitor connected with the opposite end of said tuning inductance unit from said primary winding.

4. In a multiple wave band switching system, the combination as defined in claim 3 further characterized by the fact that the primary resonating capacitor connection includes a tuning capacitor in parallel relation with each of the primary winding sections providing resonance therein below the adjusted tuning range of the inductance unit and the secondary circuit.

5. In a tuning system for a multiple wave band radio receiver, the combination with a primary circuit and a secondary circuit having a variable tuning capacitor, of an inductance unit, means providing a fixed connection for said secondary circuit with one end of said inductance unit, means providing a fixed connection for the primary circuit With the opposite end of said inductance unit, a selector switch having a plurality of fixed contacts connected between sections of said inductance unit and with the first named end thereof, a separate ultra high frequency tuning unit comprising a secondary winding and a primary winding, said last named winding being connected serially in said primary circuit, a movable switch element for connecting said contacts successively to ground and said end contact to the secondary of the separate tuning unit, a second movable contact element for said switch and fixed contacts associated therewith providing selective trimmer capacitor connections with said winding sections in the secondary circuit, and means including certain of said movable contact elements further providing a parallel coupling connection progressively along said inductance unit for said primary circuit.

7 6. In a tuning'system for a multiple wave band radio receiver, the combination as defined in claim 5 further characterized by the fact that the primary winding of the ultra high frequency tuning unit provides a low frequency primary for the lowest wave band and that a separate high frequency primary winding is provided for said wave band and coupled to the end of the inductance unit to which the secondary circuit is connected.

7. In a multiple wave band radio receiving system, the combination with a primary circuit and a secondary circuit including a tuning capacitor,

of a tuning inductance unit comprising a series of coaxial Winding sections connected at one end with said tuning capacitor and at the opposite end with the primary circuit, a plurality of trimmer capacitors each having an electrode connected to ground and a control switch having a rounding segment movable progressively to connect said winding sections to ground and dividing said winding sections between said primary and secondary circuits, means for maintaining a single one of said windings in the primary circuit, a switch segment progressively movable with said first named segment to connect a predetermined one of said trimmer capacitors across a predetermined portion of the tuning inductance in the secondary circuit, and a third movable segment in said switch providing a primary resonating capacitor connection for said tuning inductance. 8. In a multiple wave band' radio receiving system, the combination as defined in claim 7 further characterized by the fact that the winding section providing the primary for the lowest Wave band is provided with a tuning capacitor andthat said tuning capacitor provides coupling means for the primary winding sections in the higher frequency Wave bands with said first named primary winding.

9. In a coupling system for high frequency circuits, the combination with a high frequency primary circuit and a high frequency secondary circuit, of a single coil having a plurality of sections, one end of said coil being connected to the secondary circuit, means providing a ground connection between an intermediate tap on said coil common to both the primary and secondary circuits, means for tuning said secondary circuit, grounded means for tuning a plurality of said sections, means for selectively connecting said grounded tuning means each with one of said sections, means for adjusting said ground connection along said coil to vary the number of sections included in the secondary circuit, means for maintaining a connection for the primary circuit with a single one of said coil sections adjacent to and coupled with a coil in the second- "ary circuit, a fixed primary winding in said primary circuit capacity coupled to the opposite end of said coil from the secondary circuit connection, said last named means providing a bridging connection along the coil selectively to connect the primary winding in parallel with each of said plurality of coil sections thereby to include said coil sections in the primary circuit, an ultra high frequency tuning unit having a secondary winding, a primary Winding coupled therewith and connected in series with said last named primary winding, and means for connecting said secondary winding with the secondary terminal end section of said coil, and a separate primary winding in series with said first and second named primary windings providing coupling with said section of the coil 10. In a coupling system for high frequency circuits, the combination with a high frequency primary circuit and a high frequency secondary circuit, of a single coil having a plurality of sections, one end of said coil being connected to the secondary circuit, means providing a ground connection between an intermediate tap on said coil common to both the primary and secondary circuits, means for tuning said secondary circuit, grounded means for tuning a plurality of said sections, means for selectively connecting said tuning means each with one of said sections, means for adjusting said ground connection along said coil to vary the number of sections included in the secondary circuit, means for maintaining a connection for the primary circuit with a single one of said coil sections adjacent to and coupled with a coil in the secondary circuit, a fixed primary winding in said primary circuit capacity coupled to the opposite end of said coil from the secondary circuit connection, and said last named means providing a connection with said fixed primary winding to connect it in parallel with each of said coil sections included in the primary circuit. 7

11. In a coupling system for high frequency circuits, the combination with high frequency primary and secondary circuits, of an inductance unit having a plurality of sections, one end of said unit being connected to the secondary circuit, means providing a ground connection between an intermediate tap on said unit common to both the primary and secondary circuits, means for tuning said secondary circuit, means for adjusting said ground connection along said coil to vary the number of sections included in the secondary circuit, means for maintaining a connectionv for the primary circuit with a single one of said coil sections, and means providing a primary winding coupled to said first named end of the inductance unit, said winding being eifective in theultra high frequency tuning ranges of said system.

12. In a multiple wave band radio receiver comprising a radio frequency amplifier tube and a first detector tube, of a coupling system therefor comprising a primary circuit connected with the radio frequency amplifier tube and including a high frequency primary winding, a second primary winding and a low frequency primary winding in series in the anode circuit of the radio frequency amplifier tube, means providing a tunable secondary circuit connected with said detector and including a plurality of coaxial winding sections forming a tuning inductance lying between said high frequency and low frequency primary windings, means for capacity coupling said low frequency primary winding with the adjacent end of said secondary tuning inductance, switching means for grounding the secondary tuning inductance at said end and between the winding sections, a high frequency tuning unit having a secondary winding coupled with the second primary winding, switching means for connecting said secondary winding with the high frequency end of said tuning inductance unit in parallel therewith, switching means for progressively applying trimmer capacitor connections to said winding sections for initially tuning the secondary circuit in each of a plurality of wave bands, switching means for coupling said low frequency primary winding selectively with each of said winding sections in parallel, and means for conjointly operating said switching means in predetermined relation to each other.

13. In a multiple wave band radio receiver, an interstage coupling system comprising a primary circuit including a high frequency primary winding, a second primary winding and a low frequency primary winding in series, means providing a tunable secondary circuit including a plurality of coaxial winding sections forming a tuning inductance lying between said high frequency and low frequency primary windings, means for capacity coupling said low frequency primary winding with the adjacent end of said secondary tuning inductance, switching means for grounding the secondary tuning inductance at said end and between the winding sections, a high frequency tuning unit having a secondary winding coupled with the second primary winding, switching means for connecting said secondary winding with the high frequency end of said tuning inductance unit in parallel therewith, switching means for progressively applying trimmer capacitor connections to said winding sections for initially tuning the secondary circuit in each of a plurality of wave bands, switching means for coupling said low frequency primary winding selectively with each of said winding sections in parallel, and means for conjointly operating said switching means in predetermined relation to each other.

14. In a multiple wave band radio receiving system, the combination with a primary circuit, and a tunable secondary circuit, of a tuning inductance comprising a series of coaxial winding sections connected at one end with said secondary circuit and having one of said sections at the opposite end connected with the primary circuit, means for progressively connecting a plurality of said sections each in parallel with said last named section to receive signal energy therefrom, said means comprising a switch having fixed contacts connected between said winding sections, a contact element movable with respect I to and progressively in engagement with said contacts, and a second contact element movable conjointly with the first contact element to progressively ground one of said contacts in advance of said first contact element.

- JOHN D. REID. 

